[MTD] slram: Handle negative devlength correctly
[MTD] slram: Handle negative devlength correctly

A negative devlength won't get noticed and clean up:

Signed-off-by: Roel Kluin <aa9c6213291cec1ff07688554fb7b904b9ffe4e3@gmail.com>
Signed-off-by: David Woodhouse <b460d66aaf00c296a3db1c1d9eeafc081d5f7d70@intel.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas